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Tropical Storm Philippe Discussion Number  49
NWS National Hurricane Center Miami FL       AL172023
1100 AM AST Thu Oct 05 2023
 
Philippe's low-level circulation remains broad this morning with 
most of the associated deep convection located within the eastern 
semicircle.  Despite the continued disorganized structure, an Air 
Force Reserve Hurricane Hunter mission this morning measured peak 
850-mb flight-level winds of 56 kt and SFMR surface winds of 40-45 
kt.  Based on these data, Philippe's initial intensity is raised to 
45 kt.

The latest fixes suggest that Philippe is moving just west of due 
north (355 degrees) at 10 kt.  This northward motion, with an 
increase in forward speed, is expected to continue through Saturday 
while Philippe moves over the western Atlantic between a deep-layer 
trough east of Florida and a mid-level high over the central 
Atlantic.  A north-northwestward turn is likely to occur as the 
cyclone is approaching Atlantic Canada or eastern New England, due 
to a larger trough approaching from the west.  Since Philippe may 
interact with a baroclinic zone and a developing non-tropical low 
to its west in another day or two, the nuances of the track 
forecast still need to be worked out, but nearly all of the track 
guidance agrees on the forecast scenario described above.  The NHC 
forecast is close to the HCCA consensus aid and brings the center 
to the coast of Nova Scotia, New Brunswick, or eastern Maine 
between 60 and 72 hours.  The center should then be absorbed by a 
broad area of low pressure to its west over Quebec some time on 
Sunday.

Little change in intensity is expected during the next day or two, 
particularly since model guidance suggests that the shear over 
Philippe could strengthen further.  Despite the shear, some 
additional strengthening is possible in about 48 hours when 
Philippe could receive an injection of baroclinic energy from the 
trough located east of Florida.  That process should also 
kick-start extratropical transition, and the NHC forecast shows the 
transition complete by 60 hours (late Saturday) when Philippe is 
located offshore of Nova Scotia.  Weakening is forecast once 
Philippe moves inland, and it's likely that the strongest winds from 
the system will continue to occur on the eastern side of the 
circulation, primarily over parts of Atlantic Canada.
 
 
KEY MESSAGES:
 
1. Tropical storm conditions are expected on Bermuda beginning
early Friday morning, and a Tropical Storm Warning remains in 
effect.  Heavy rainfall will also begin to affect the island today, 
which could produce flash-flooding.
 
2. Philippe is expected to move over portions of Atlantic Canada and
eastern New England as a post-tropical cyclone this weekend.  
Regardless of Philippe's intensity or structure, interests in those 
areas should be prepared for the possibility of strong winds and 
heavy rainfall and monitor statements from their local weather 
office.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/1500Z 25.6N  66.3W   45 KT  50 MPH
 12H  06/0000Z 27.7N  66.4W   45 KT  50 MPH
 24H  06/1200Z 30.9N  66.3W   45 KT  50 MPH
 36H  07/0000Z 34.2N  66.6W   50 KT  60 MPH
 48H  07/1200Z 37.6N  66.6W   50 KT  60 MPH
 60H  08/0000Z 41.8N  66.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  08/1200Z 47.4N  68.0W   40 KT  45 MPH...POST-TROP/INLAND
 96H  09/1200Z...DISSIPATED
 
$$
Forecaster Berg
 
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